The Clinical Epilepsy Section continues to study the clinical pharmacology of old and new antiepileptic drugs. Special emphasis has been placed on studies of two new antiepileptic compounds, progabide and flupirtine. Progabide has been studied pharmacokinetically in normal volunteers, whereas flupirtine is being evaluated both clinically and pharmacologically in patients with either complex partial or absence seizures. Flupirtine is especially promising in models of epilepsy and preliminary clinical results are encouraging. Drug interactions continue to be a major pharmacologic interest of the Section. Most recently, the interaction between phenytoin and carbamazepine has been evaluated using mass spectrometry methodology. Other studies recently completed include the interaction of phenytoin and primidone, as well as valproate and phenobarbital. The pharmacologic evaluation of these drugs is coupled with efficacy studies, carried out by intensive monitoring techniques including videotape analysis of epileptic seizures with simultaneous telemetered EEG recording, and daily determination of antiepileptic drug levels.